The island is dominated by a maritime climate with quite narrow temperature differences between seasons. Politically, the island is part of the United Kingdom of Great Britain and Northern Ireland, with Great Britain constituting most of the United Kingdom's territory.[10] Most of England, Scotland, and Wales are on the island. The term Great Britain often extends to include surrounding islands that form part of England, Scotland, and Wales.[13] Politically, Great Britain is not a nation-state/country but those born on the island and naturalised residents are known as Britons and are commonly referred to as 'British' citizens/nationals.

The earliest known name for Great Britain is Albion (Greek: Ἀλβίων) or insula Albionum, from either the Latin albus meaning "white" (referring to the white cliffs of Dover, the first view of Britain from the continent) or the "island of the Albiones", first mentioned in the Massaliote Periplus in the 6th century BC, and by Pytheas.[18]

Pliny the Elder (c. AD 23–79) in his Natural History records of Great Britain: "Its former name was Albion; but at a later period, all the islands, of which we shall just now briefly make mention, were included under the name of 'Britanniæ.'"[20]

The name Britain descends from the Latin name for Britain, Britannia or Brittānia, the land of the Britons. Old FrenchBretaigne (whence also Modern FrenchBretagne) and Middle EnglishBretayne, Breteyne. The French form replaced the Old EnglishBreoton, Breoten, Bryten, Breten (also Breoton-lond, Breten-lond). Britannia was used by the Romans from the 1st century BC for the British Isles taken together. It is derived from the travel writings of the ancient GreekPytheas around 320 BC, which described various islands in the North Atlantic as far north as Thule (probably Norway).

Marcian of Heraclea, in his Periplus maris exteri, described the island group as αἱ Πρεττανικαὶ νῆσοι (the Prettanic Isles).[21]

The Greco-Egyptian scientist Ptolemy referred to the larger island as great Britain (μεγάλης Βρεττανίας - megális Brettanias) and to Ireland as little Britain (μικρής Βρεττανίας - mikris Brettanias) in his work Almagest (147–148 AD).[23] In his later work, Geography (c. 150 AD), he gave these islands the names Alwion, Iwernia, and Mona (the Isle of Man),[24] suggesting these may have been names of the individual islands not known to him at the time of writing Almagest.[25] The name Albion appears to have fallen out of use sometime after the Roman conquest of Great Britain, after which Britain became the more commonplace name for the island called Great Britain.[18]

After the Anglo-Saxon period, Britain was used as a historical term only. Geoffrey of Monmouth in his pseudohistoricalHistoria Regum Britanniae (c. 1136) refers to the island of Great Britain as Britannia major ("Greater Britain"), to distinguish it from Britannia minor ("Lesser Britain"), the continental region which approximates to modern Brittany, which had been settled in the fifth and sixth centuries by Celtic immigrants from the British Isles.[26] The term Great Britain was first used officially in 1474, in the instrument drawing up the proposal for a marriage between Cecily the daughter of Edward IV of England, and James the son of James III of Scotland, which described it as "this Nobill Isle, callit Gret Britanee". It was used again in 1604, when King James VI and I styled himself "King of Great Brittaine, France and Ireland".

Great Britain refers geographically to the island of Great Britain, politically to England, Scotland and Wales in combination.[27] However, it is sometimes used loosely to refer to the whole of the United Kingdom.[28]

The term Britain, as opposed to Great Britain, has been used to mean the United Kingdom formally, for example in official government yearbooks between 1975 and 2001.[29] Since 2002, however, the yearbooks have only used the term "United Kingdom".[30]

On the Internet, .uk is the country code top-level domain for the United Kingdom. A .gb top-level domain was used to a limited extent, but is now obsolete because the domain name registrar will not take new registrations.

Prima Europe tabula. A copy of Ptolemy's 2nd century map of Roman Britain

The Romans conquered most of the island (up to Hadrian's Wall, in northern England) and this became the Ancient Roman province of Britannia. In the course of the 500 years after the Roman Empire fell, the Britons of the south and east of the island were assimilated or displaced by invading Germanic tribes (Angles, Saxons, and Jutes, often referred to collectively as Anglo-Saxons). At about the same time, Gaelic tribes from Ireland invaded the north-west, absorbing both the Picts and Britons of northern Britain, eventually forming the Kingdom of Scotland in the 9th century. The south-east of Scotland was colonised by the Angles and formed, until 1018, a part of the Kingdom of Northumbria. Ultimately, the population of south-east Britain came to be referred to as the English people, so-named after the Angles.

Germanic speakers referred to Britons as Welsh. This term came to be applied exclusively to the inhabitants of what is now Wales, but it also survives in names such as Wallace and in the second syllable of Cornwall. Cymry, a name the Britons used to describe themselves, is similarly restricted in modern Welsh to people from Wales, but also survives in English in the place name of Cumbria. The Britons living in the areas now known as Wales, Cumbria and Cornwall were not assimilated by the Germanic tribes, a fact reflected in the survival of Celtic languages in these areas into more recent times.[37] At the time of the Germanic invasion of Southern Britain, many Britons emigrated to the area now known as Brittany, where Breton, a Celtic language closely related to Welsh and Cornish and descended from the language of the emigrants, is still spoken. In the 9th century, a series of Danish assaults on northern English kingdoms led to them coming under Danish control (an area known as the Danelaw). In the 10th century, however, all the English kingdoms were unified under one ruler as the kingdom of England when the last constituent kingdom, Northumbria, submitted to Edgar in 959. In 1066, England was conquered by the Normans, who introduced a Norman-speaking administration that was eventually assimilated. Wales came under Anglo-Norman control in 1282, and was officially annexed to England in the 16th century.

On 20 October 1604 King James, who had succeeded separately to the two thrones of England and Scotland, proclaimed himself "King of Great Brittaine, France, and Ireland".[38] When James died in 1625 and the Privy Council of England was drafting the proclamation of the new king, Charles I, a Scottish peer, Thomas Erskine, 1st Earl of Kellie, succeeded in insisting that it use the phrase "King of Great Britain", which James had preferred, rather than King of Scotland and England (or vice versa).[39] While that title was also used by some of James's successors, England and Scotland each remained legally separate countries, each with its own parliament, until 1707, when each parliament passed an Act of Union to ratify the Treaty of Union that had been agreed the previous year. This created a single kingdom out of two, with a single parliament, with effect from 1 May 1707. The Treaty of Union specified the name of the new all-island state as "Great Britain", while describing it as "One Kingdom" and "the United Kingdom". To most historians, therefore, the all-island state that existed between 1707 and 1800 is "Great Britain" or the "Kingdom of Great Britain".

Great Britain lies on the European continental shelf, part of the Eurasian Plate. Situated off the north-west coast of continental Europe, it is separated from the mainland by the North Sea and by the English Channel, which narrows to 34 km (18 nmi; 21 mi) at the Straits of Dover.[40] It stretches over about ten degrees of latitude on its longer, north-south axis and occupies an area of 209,331 km2 (80,823 sq mi), excluding the smaller surrounding islands.[41] The North Channel, Irish Sea, St George's Channel and Celtic Sea separate the island from the island of Ireland to its west.[42] The island is physically connected with continental Europe via the Channel Tunnel, the longest undersea rail tunnel in the world, completed in 1993. The island is marked by low, rolling countryside in the east and south, while hills and mountains predominate in the western and northern regions. It is surrounded by over 1,000 smaller islands and islets. The greatest distance between two points is 968.0 km (6011⁄2 mi) (between Land's End, Cornwall and John o' Groats, Caithness), 838 miles (1,349 km) by road.

The English Channel is thought to have been created between 450,000 and 180,000 years ago by two catastrophic glacial lake outburst floods caused by the breaching of the Weald-Artois Anticline, a ridge that held back a large proglacial lake, now submerged under the North Sea.[43] Around 10,000 years ago, during the Devensian glaciation with its lower sea level, Great Britain was not an island, but an upland region of continental northwestern Europe, lying partially underneath the Eurasian ice sheet. The sea level was about 120 metres (390 ft) lower than today, and the bed of the North Sea was dry and acted as a land bridge, now known as Doggerland, to the Continent. It is generally thought that as sea levels gradually rose after the end of the last glacial period of the current ice age, Doggerland became submerged beneath the North Sea, cutting off what was previously the British peninsula from the European mainland by around 6500 BC.[44]

Great Britain has been subject to a variety of plate tectonic processes over a very extended period of time. Changing latitude and sea levels have been important factors in the nature of sedimentary sequences, whilst successive continental collisions have affected its geological structure with major faulting and folding being a legacy of each orogeny (mountain-building period), often associated with volcanic activity and the metamorphism of existing rock sequences. As a result of this eventful geological history, the island shows a rich variety of landscapes.

The oldest rocks in Great Britain are the Lewisian gneisses, metamorphic rocks found in the far north west of the island and in the Hebrides (with a few small outcrops elsewhere), which date from at least 2,700 Ma (Ma = million years ago). South of the gneisses are a complex mixture of rocks forming the North West Highlands and Grampian Highlands in Scotland. These are essentially the remains of folded sedimentary rocks that were deposited between 1,000 Ma and 670 Ma over the gneiss on what was then the floor of the Iapetus Ocean.

At the present time the north of the island is rising as a result of the weight of Devensian ice being lifted. Southern and eastern Britain is sinking, generally estimated at 1 mm (1/25 inch) per year, with the London area sinking at double the speed partly due to the continuing compaction of the recent clay deposits.

Animal diversity is modest, as a result of factors including the island's small land area, the relatively recent age of the habitats developed since the last glacial period and the island's physical separation from continental Europe, and the effects of seasonal variability.[46] Great Britain also experienced early industrialisation and is subject to continuing urbanisation, which have contributed towards the overall loss of species.[47] A DEFRA (Department for Environment, Food and Rural Affairs) study from 2006 suggested that 100 species have become extinct in the UK during the 20th century, about 100 times the background extinction rate. However, some species, such as the brown rat, red fox, and introduced grey squirrel, are well adapted to urban areas.

There are many species of fungi including lichen-forming species, and the mycobiota is less poorly known than in many other parts of the world. The most recent checklist of Basidiomycota (bracket fungi, jelly fungi, mushrooms and toadstools, puffballs, rusts and smuts), published in 2005, accepts over 3600 species.[67] The most recent checklist of Ascomycota (cup fungi and their allies, including most lichen-forming fungi), published in 1985, accepts another 5100 species.[68] These two lists did not include conidial fungi (fungi mostly with affinities in the Ascomycota but known only in their asexual state) or any of the other main fungal groups (Chytridiomycota, Glomeromycota and Zygomycota). The number of fungal species known very probably exceeds 10,000. There is widespread agreement among mycologists that many others are yet to be discovered.

In the Late Bronze Age, Britain was part of a culture called the Atlantic Bronze Age, held together by maritime trading, which also included Ireland, France, Spain and Portugal. In contrast to the generally accepted view[70] that Celtic originated in the context of the Hallstatt culture, since 2009, John T. Koch and others have proposed that the origins of the Celtic languages are to be sought in Bronze Age Western Europe, especially the Iberian Peninsula.[71][72][73][74] Koch et al.'s proposal has failed to find wide acceptance among experts on the Celtic languages.[70]

All the modern Brythonic languages (Breton, Cornish, Welsh) are generally considered to derive from a common ancestral language termed Brittonic, British, Common Brythonic, Old Brythonic or Proto-Brythonic, which is thought to have developed from Proto-Celtic or early Insular Celtic by the 6th century AD.[75] Brythonic languages were probably spoken before the Roman invasion at least in the majority of Great Britain south of the rivers Forth and Clyde, though the Isle of Man later had a Goidelic language, Manx. Northern Scotland mainly spoke Pritennic, which became Pictish, which may have been a Brythonic language. During the period of the Roman occupation of Southern Britain (AD 43 to c. 410), Common Brythonic borrowed a large stock of Latin words. Approximately 800 of these Latin loan-words have survived in the three modern Brythonic languages. Romano-British is the name for the Latinised form of the language used by Roman authors.

British English is spoken in the present day across the island, and developed from the Old English brought to the island by Anglo-Saxon settlers from the mid 5th century. Some 1.5 million people speak Scots—a variety of English which some consider to be a distinct language.[76][77] An estimated 700,000 people speak Welsh,[78] an official language in Wales.[79] In parts of north west Scotland, Scottish Gaelic remains widely spoken. There are various regional dialects of English, and numerous languages spoken by recent immigrant populations.

^The political definition of Great Britain – that is, England, Scotland and Wales combined – includes a number of offshore islands such as the Isle of Wight, Anglesey and Shetland which are not part of the geographical island of Great Britain. Those three countries combined have a total area of 234,402 km2 (90,503 sq mi).[6]

^"Population Estimates"(PDF). National Statistics Online. Newport, Wales: Office for National Statistics. 24 June 2010. Archived from the original(PDF) on 14 November 2010. Retrieved 24 September 2010.

^Britain, Oxford English Dictionary, Britain:/ˈbrɪt(ə)n/ the island containing England, Wales, and Scotland. The name is broadly synonymous with Great Britain, but the longer form is more usual for the political unit.

^Great Britain, Oxford English Dictionary, Great Britain: England, Wales, and Scotland considered as a unit. The name is also often used loosely to refer to the United Kingdom.

^Definitions and recommended usage varies. For example, the Oxford English Dictionary defines Britain as an island and Great Britain as a political unit formed by England, Scotland and Wales.[11][12] whereas the Cambridge Guide to English Usage gives Britain as "familiar shorthand for Great Britain, the island which geographically contains England, Wales and Scotland"

^4.20 provides a translation describing Caesar's first invasion, using terms which from IV.XX appear in Latin as arriving in "Britannia", the inhabitants being "Britanni", and on p30 "principes Britanniae" (i.e., "chiefs of Britannia") is translated as "chiefs of Britain".

^O Corrain, Donnchadh , Professor of Irish History at University College Cork (1 November 2001). "Chapter 1: Prehistoric and Early Christian Ireland". In Foster, R F. The Oxford History of Ireland. Oxford University Press. ISBN0-19-280202-X.

^Oxford English Dictionary, Oxford: Oxford University Press, Great Britain: England, Wales, and Scotland considered as a unit. The name is also often used loosely to refer to the United Kingdom.
Great Britain is the name of the island that comprises England, Scotland, and Wales, although the term is also used loosely to refer to the United Kingdom. The United Kingdom is a political unit that includes these countries and Northern Ireland. The British Isles is a geographical term that refers to the United Kingdom, Ireland, and surrounding smaller islands such as the Hebrides and the Channel Islands.